FE 212 Biochemistry Exam Questions

EXAM QUESTIONS =FIRST MIDTERM= 1.Choose the wrong statement on building blocks of biopolymers a) amino acids are monomers of proteins b) glucose is monomer of carbohydrates c) nucleotides are monomers of nucleic acids d) fatty acids are monomers of lipids 2. 100ml of 0.1 M NaOH is added to 100mL of 0.2M isoelectric leucine (pK₁=2.36 and pK₂=9.60) The resulting mixture has a pH equal to: a)2.4 b)5.9 c)9.6 d)10.6 3. Which of the following is not a true statement regarding the difference between DNA and RNA? a)RNa contains adenine,guanine,cytosine and uracil,while DNA only contains thymine b)The sugar is RNA is ribose while DNA contains the sugar deoxyribose c)DNA is found in a helical structure, while RNA is usually single stranded d) In DNA uracil is absent, in RNA there is no thymine 4. Which of the following is not a pyrimidine? a)thymine b)guanine c)cytosine d)uracil 5. Consider the polypeptide whose primary structure is as follows: Ala-Cys-Phe-Pro-Lys-Arg-Trp-Cys What are the fragments after partial hydrolysis by chymotrypsin? (Chymotrysin: C-side of Rn= Phe,Trp,Tyr,Leu; Rn+1≠Pro) a) Ala,Phe,Lys,Cys,Pro,Arg Trp,Cys b) Ala,Phe,Cys Pro,Lys,TRp,Arg Cys c) Ala,Pro,Trp,Arg,Cys,Phe,Lys Cys d) None of them 6. Which of the following sugars is not a disaccharide a)sucrose b)galactose c)lactose d)maltose 7. What is the net charge of leucine at pH=7.5? (pK₁=2.36 and pK₂=9.60) a)+1 b)-1 c)0 d)none of them 8. How many optical isomers of isoleucine are available? a)2 b)4 c)1 d)none of them 9. Choose the wrong statement on amino acid side chains a) gly,ala,val,leu are amino acids with aliphatic R-groups

b) phe,tyr,trp have aromatic R-groups c) asp,glu have acidic R-groups d) ser,thr are amino acids with sulfur containing R-groups 10. More than 99% by weight of living matter is made up of the four element,namely a) H,O,C,P b) H,O,N,C c) H,O,S,C d)H,O,C,Fe 11. The selection of raw materials for biological systems in the course of evolution was determined by a)fitness b)availability c)both fitness and availability d)none of them 12. Choose the wrong statement on denaturation of proteins a) denaturation destroys the natural conformation of a protein b) urea and guanidine HCI are denaturating agents c)during denaturation all the bonds are broken d) denaturation and hydrolysis is carried out for composition analysis 13. Disulfide bonds in the protein tertiary structure are broken by a)oxidation b)reduction c)urea d)guanidine HCI 14. Which of the following statements on nucleus is not true? a) replication and transcription takes place in the nucleus b) the outer membrane of the nuclear membrane is continuous with endoplasmic reticulum c) replication,transcription and translation takes place in the nucleus d) nucleus is structurally defined by a nuclear envelope, a double membrane 15. Prokaryotic cells a) have no organelles b) do not have mitochondria c) have cell Wall,cell membrane and cytosol d) all of the above 16. Which of the following statements on classification of cell is not true? a) photosynthesis cells produce glucose b) autotrophs can survive using organic nutrients c) heterotrophic cell use glucose d) aerobes live in the presence of oxygen 17. Mitochondria a) are the second largest organelles b) are surrounded by single membrane c) are present in animal and plant cells d) none of the above 18. Facultative organism can survive a) in the absence of O₂ b) in the presence of O₂ c) in the absence and presence of O₂ d) only using CO₂

19. Enzymes can act to catalyze a reaction by; a) lowering the activation energy for a reaction b) lowering the standard reduction potential for a reaction c) raising the activation energy for a reaction d) raising the standard reduction potential for a reaction 20. The ratio of Vmax/Km describes; a) the maximum reaction rate fort he enzyme b) the affinity of an enzyme for a substrate c) describes the efficiency of the enzyme d) none of the above 21. Figure shows the dependence of an enzyme’s rate v (in µmole/min) as a function of substrate concentration (in mM). It also shows the dependence of the rate in the presence of an inhibitör present 0.5 mM. What are the Vmaz,Km and Ki values of inhibited reaction? ________Vmax (µmole/min)_____Km (mM)_________Ki(mM) a) 0.5 1 0.5 b) 2 2 0.5 c) 1 0.5 2 d) 2 2 1 22. Types of reversible enzyme inhibiton can be classified as; a) competitive and anticompetitive b) noncompetitive and competitive c) competitive, uncompetitive and noncompetitive d) anticompetitive, noncompetitive and uncompetitive 23. The Michaelis-Menten constant, Km; a) describes the affinity of an enzyme for the substrate, if Km is small, the enzyme has little affinity for the subsrate b) describes the maximum reaction rate for an enzyme c) describes the efficiency of an enzyme

d) describes the affinity of an eznyme for the substrate, if Km is large then the enzyme has less affinity for the substrate 24. In the formation of an eznyme-substrate complex, the reaction rate; a) tends to maximum Vmax, when the substrate concentration [S] << Km b) dependes solely on the Michaelis constant, Km c) is highly dependent on the substrate concentration [S], with vi=Vmax/2 if [S]=Km d) goes to vi=Vmax.Km when the substrate concentration is very small 25. Noncompetitive inhibiton; a) increases Km b) increases Vmax c) decreases Km d) decreases Vmax 26. Which of the following is not true statement about enzymes? a) enzyme activity is enhanced by rising pH b) enzyme activity is enhanced by rising temperature, to a point c) very high temperatures tend to denature enzymes d) enzyme activity is influenced by concentration of substrate and enzyme 27. Irreversible inhibiton; a) involves a strong covalent bond between the enzyme and the inhibitor b) involves a transfer of a proton c) is usually affected using van der walls interactions d) none of them above 28. Alcohol dehydrogenase a) catalyzes the oxidation of ethanol b) catalyzes the oxidation of methanol c) requires Zn²⁺ as a cofactor d) all are correct 29. A reaction will ocur spontaneously if; a) there is an increase in entropy b) there is an increase in free energy c) there is a decrease in free energy d) hear is absorbed 30. For the oxidation of ethanol to acetaldehyde; a) NADP⁺ is the electron acceptor b) NAD⁺ is the elecetron acceptor c) FAD is the electron acceptor d) none of them is true 31. When a mixture of glucose-6-phosphate and fructose-6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose-6- phosphate as fructose-6-phosphate. Which one of the following statements is most nearly correct, when applied to the reaction below? (R=8.315 J/mol.K and T=298K) Glucose-6-phosphate ↔ fructose-6-phosphate a) ∆Gº is 1.7 kJ/mol b) ∆Gº is -1.7 kJ/mol c) ∆Gº is zero d) none 32. There are three stages of catabolism and in stage I a) lipids are converted into glycerol and fatty acids

b) proteins are converted to pyruvate c) carbohydrates are converted into pyruvate d) glucose is converted into pyruvate 33. There are two phases of metabolism, and a) catabolism is reductive in nature b) anabolism is oxidative in nature c) amphibolic pathway serves for both anabolism and catabolism d) both anabolism and catabolism produces energy 34. Which is the true electron acceptor fort he oxidation of the following organic substance ‘R-CH₂CH₂-R’ a) NAD⁺ b) NADP⁺ c) FAD d) none of them 35. A cofactor can be best described as a) an inorganic compound that inhibits substrate binding b) an inorganic compound that promotes subsrate binding c) an organic substrate that promotes binding of an additional subsrate d) an organic or inorganic compound that activates an eznyme 36. Which of the following statements is not true on electron carriers a) NAD⁺ is composed of two riboses, one adenine, one nicotinamide ring and two phosphate groups b) FAD is composed of isoalloxazine ring, two sugar moiety, one guanine and two phosphate groups c) Both NAD⁺ and FAD carriers two electrons d) NAD⁺ takes electrons from the same carbon 37. Which of the followings is high,energy biomolecule a) ATP b) acetyl-CoA c) NADH d) all of them 38. Choose the wrong statement on metabolism a) metabolism is the sum of all chemical reactions taking place within the cell b) the reaction are all organic reactions c) all the reaction are at equilibrium within the cell d) all the reactions are enzyme,catalyzed reactions 39. Both catabolism and anabolism proceeds in a stepwise manner through many intermediates. Which of the following enzyme systems is not present fort he squences of consecutive enzyme,catalyzed reactions? a) free eznyme system b) multienzmye complex c) cytosolic enzyme system d) membrane-bound enzyme 40. Amphibolic pathway a) is a common central pathway b) serves for only catabolism c) releases one molecule of CO₂ c) releases two molecule of H₂O

=SECOND MIDTERM= 1. Which of the following statements about glucose metabolism is not true? a) glucose is converted to pyruvate in cytosol b) each molecule of glucose produces net 2 ATP during glycolysis c) glucose is converted to lactate, which is oxidized in further pathways d) formation of glucose from lactate takes place in the liver 2. The oxidation of 3 mol of glucose by pentose phosphate pathway may result in the production of; a) 2 mol of pentose, 4 mol of NADPH and 8 mol of CO₂ b) 3 mol of pentose, 4 mol of NADPH and 3 mol of CO₂ c) 3 mol of pentose, 6 mol of NADPH and 3 mol of CO₂ d) 4 mol of pentose, 3 mol of NADPH and 3 mol of CO₂ 3. In nonoxidative cycle of pentose phosphate pathway a) ketose is always elctron acceptor b) transketolase catalyzes the transfer of 2-C unit where as transaldolase catalyzes 3-C unit transfer c) cycle operates when more NADPH is required than ribulose-5-phosphate d) all except (a) is true 4. Epinephrine a) increases glucose concentration in blood b) activates cAMP formation in muscle c) activates gluconeogenesis d) all of the above is true 5. Metabolism of amino acids a) requires transaminases b) depends on the availability of an α-keto acid, oxaloacetate c) supplies reactants for gluconeogenesis d) all except (b) are correct 6. The enzyme pyruvate kinase (Liver form) a) is activated by fructose and inhibited by ATP b) is activated by ATP and inhibited by fructose 1,6-diphosphate c) is activated by fructose 1,6-diphosphate and inhibited by ATP d) is inhibited by fructose 1,6-diphosphate 7. An enzyme used in both glycolysis and gluconeogenesis is a) 3-phosphoglycerate kinase b) glucose-6-phosphatase c) hexokinase d) pyruvate kinase 8. All of the following enzymes involved in the flow of carbon from glucose to lactate are involved in the reversal of this flow except; a) aldolase b) enolase c) phosphofructokinase d) phosphoglucoisomerase 9. Gluconeogenesis;

a) can result in the conversion of protein into blood glucose b) helps to reduce blood glucose after a carbohyrate-rich meal c) is activated by the hormone insülin d) requires the enzyme hexokinase 10. Which of the following statemnets about hte pentose phosphate pathway is incorrect? a) it generates CO₂ from C-1 of glucose b) it involves the generation of energy c) it is principally directed toward the generation of NADPH d) it is stimulated by increased concentration of NADP 11. Choose the wrong statement a) cori cycle is one way process to produce glucose in liver b) NADH/NAD ratio is high during glycolysis c) NADH/NAD ratio is low during glycolysis d) NADH/NAD ratio is low during gluconeogenesis 12. Which enzymes of the glycogen metabolic patyway does phosphorylase kinase regulate a) it activates glycogen phosphorylase and glycogen synthase b) it inactivates glycogen phosphorylase and glycogen synthase c) it activates glycogen phosphorylase and inactivates glycogen synthase d) it inactivates glycogen phosphorylase and activates glycogen synthase 13. Hormone produced in response to high blood sugar is; a) epinephrine b) insülin c) glucagon d) none of them 14. How is PEP(phosphoenol pyruvate) generated from pyruvate during gluconeogenesis a) pyruvate is converted to oxaloacetate, and then PEP. Both reactions are coupled to ATP hydrolysis b) pyruvate is converted to oxaloacetate, and then PEP. Both reactions are coupled to GTP hyrolysis c) pyruvate is converted to oxaloacetate, which is coupled to ATP hyrolysis and then which is coupled to GTP hyrolysis d) pyruvate is converted to oxaloacetate, which is coupled to GTP hydrolysis and then which is coupled to ATP hydrolysis 15. Choose the wrong enzyme-cofactor pair a) pyruvate carboxylase-biotin b) alcohol dehydrogenesa- Zn⁺² c) pyruvate kinase- Mg⁺² d) transaminase-thiamine pyrophosphate 16. Citric acid cycle turns a) two times for glucose b) two times for succinic acid c) one time for alanine d) all of them are correct 17. Choose the wrong statement a) Citric acid cycle takes place in the mitochondrial matrix b) Citric acid cycle is catalyzed by eight enzymes